A commonly used technique within modern radio networks is Time Division Multiplexing (TDM). At the physical layer, this is known as Time Division Multiple Access (TDMA). In TDMA-based networks, the same physical channel can be shared by several different nodes. The physical channel is divided into slices of time called time slots. TDMA protocols can be used to assign a time slot to nodes in the network. These time slots can be reserved and accessed by the different nodes on a cyclical basis. Each node transmits only in its reserved time slot on a cyclical basis. For example, circuit switched TDMA-based voice systems usually allocate a single timeslot in a frame for a single voice connection for a period of time. By contrast, systems which tend to carry bursty data typically use dynamic allocation schemes to assign timeslots. For instance, Demand Assigned Multiple Access (DAMA) systems can be used to allocate timeslots on demand.
In some networks, such as a wired Ethernet network, a source node can immediately sense if its transmission has collided with another node's transmission on the wire. If a collision is not detected, the source node knows the packet has been delivered, and if a collision is detected, the source node will retry delivery.
In other networks, such as a wireless network, a source node can not directly detect whether there is a collision at a destination node. Rather, higher layer protocols must wait for the destination node to respond in another different time slot. This introduces delay (e.g., waiting for the response), inefficiency (e.g., requires another slot), and complicates recovery from a failure. This can be problematic especially when applied in systems transporting time sensitive data, such as interactive voice/video, and non-interactive data, such as one way audio/video at variable modulation and high data rates.